Method of assay for prostaglandins of the F alpha series

ABSTRACT

A method for assaying prostaglandins of the F.sub.α  series by reacting a compound of this series with a compound having the formula R--B(OH) 2  wherein R is a radical containing a fluorescent or radioactive label, isolating the reaction product and measuring the amount of fluorescence or radioactivity of the reaction product.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an assay. More particularly, the present invention relates to an assay for prostaglandins of the F.sub.α series.

2. BACKGROUND of the Prior Art

Prostaglandins of the F.sub.α series are known and are characterized by containing a C₉₉ and C₁₁ cis-diol structure in the cyclopentane ring.

For example, prostaglandin F₂.sub.α (PGF₂.sub.α) is a compound having the following structural formula ##SPC1##

Other F.sub..sub.α prostaglandins include PGF.sub. 1.sub.α and PGF₃.sub.α. Prostaglandins exist in the cells of many, if not all, animals. They exert biological activities in the body of the animal in which it is present. A simple assay for the presence of PGF.sub.α compounds, and especially PGF₂.sub.α, would be valuable for research and diagnostic purposes.

It was disclosed in J. Chrom. Sci. 56 1:129 (1971) that n-butyl boronic acid reacts with PGF₂.sub.α and the combination may be used in the GLC analysis for PGF₂.sub.α.

SUMMARY OF THE INVENTION

The present invention relates to a method for assaying for prostaglandins of the E.sub.α series comprising reacting prostaglandins of the F.sub.α series with a compound having the formula ##EQU1## where R is a radical containing a fluorescent of radioactive label, isolating the labeled reaction product, and measuring the amount of fluorescence or radioactivity of the labeled reaction product.

DETAILED DESCRIPTION OF THE INVENTION

The following general reaction is utilized by the present assay method (in this case, PGF₂.sub.α is representative of prostaglandins of the F.sub.α series). ##SPC2##

The radical R in the compound ##EQU2## can contain either a radioactive label or a fluorescent label. For example, R may be any radical containing a ¹⁴ C or ³ H or S³⁵ or I¹³¹ or I¹²⁵ or other radioactive label. A preferred radioactive label is a labeled hydrocarbon radical such as, for example, an n-butyl group labeled with ¹⁴ C or ³ H. Similarly, R could be any fluorescent radical such as, for example, in the following compounds: ##SPC3##

The reaction of the labeled boronic acid derivative and prostaglandins of the F.sub.α series takes place in conventional organic solvents such as methanol, ethanol, butanol, acetone, 2,2-dimethoxypropane, etc.

Prior to the reaction, the prostaglandin of the F.sub.α series is preferably extracted from whatever aqueous medium or biological fluid it is in by extraction with a suitable solvent, such as ethyl acetate, or by column chromatographic isolation utilizing, for example, Sephadex LH-20 or Amberlite XAD-2 columns.

The reaction of a prostaglandin of the F.sub.α series and the boronic acid derivatives may be carried out at temperatures between about 20° and 100°C and preferably at about 50°C for about 1 to about 30 minutes and preferably about 1-5 minutes.

The labeled reaction products are then isolated from the reaction mixture by any suitable analytical method including thin layer chromatography (TLC), paper chromatography, column chromatography, etc.

The isolated, labeled reaction products are then evaluated for fluorescence (if the boronic acid derivative was labeled with a fluorescent-containing radical) by conventional fluorometric techniques or for radioactivity (if the boronic acid derivative was labeled with a radical containing a radioactive species) by conventional radiation counting.

The foregoing method results in a qualitative as well as quantitative assay for prostaglandins of the F.sub.α series.

This assay may be used to determine levels of prostaglandins of the F.sub.α series including various biological systems including biological tissues, blood, urine, etc. In order to guard against loss of a prostaglandin F.sub.α in a sample, e.g. by degradation, an internal standard may be used. For example, a known amount of ¹⁴ C labeled PGF₂.sub.α may be added to the sample prior to the assay and counted at the end of the procedure. The percent reduction of ¹⁴ C PGF₂.sub.α from the known amount placed in the sample indicates the percent of PGF₂.sub.α lost during the assay procedure. Other similar internal standards may be used.

In order to minimize interference of background radiation caused by exchange of ³ H atoms (if a tritiated label is used) for ¹ H atoms in water present in the assay sample, the water remaining in the reaction sample is preferably removed by any convenient method, e.g. a deliquescent substance such as, for example, magnesium sulfate, may be added to the sample.

The following Examples are for the purpose of illustration and it is understood that the invention is not to be limited to the reagents or conditions set forth.

EXAMPLE I

Assay for PGF₂.sub.α is conducted by reacting with 10.sup.⁻⁹ g ³ H-labeled n-butyl boronic acid (10 C/m-mole) with PGF₂.sub.α at 50°C under anhydrous conditions in 2,2-dimethoxypropane for 1 minute. The reaction mixture is then spotted on silica gel TLC plates and developed in a solvent system consisting of the organic phase of ethyl acetate-glacial acetic acid-iso-octane-water in ratios of 110:20:50:100. The plates are visualized with I₂ vapor and the reaction product spot scraped and the radioactivity is measured by a standard scintillation counter. The results indicate that in excess of 90% of the PGF₂.sub.α is recovered.

EXAMPLE II

Example I is repeated in the presence of prostaglandin E₂ (PGE₂). No interference of the reaction by PGE₂ is found.

EXAMPLE III

EXAMPLE I is repeated, except the radioactive labeled boronic acid is replaced with the fluorescent compound ##SPC4##

After the labeled reaction products are separated by TLC, they are analyzed by conventional fluorescent techniques instead of radioactive counting. Similar results are obtained.

EXAMPLE IV

EXAMPLE I is repeated, except the n-butyl boronic acid is labeled with ¹⁴ C rather than ³ H. Comparable results are obtained. 

I claim:
 1. A method for assaying prostaglandins of the F.sub.α series comprising reacting a prostaglandin of the F.sub.α series with a compound having the formula ##EQU3## where R is a radical containing a fluorescent or radioactive label, isolating the labeled reaction products, and respectively measuring the amount of fluorescence or radioactivity of the labeled reaction product.
 2. The method of claim 1 wherein R contains a fluorescent label.
 3. The method of claim 1 wherein R contains a radioactive label.
 4. The method of claim 2 wherein the radioactive label is ¹⁴ C or ³ H.
 5. The method of claim 1 wherein R is a tritium labeled butyl radical.
 6. The method of claim 4 wherein the prostaglandin is prostaglandin F₂.sub.α.
 7. A method for assaying prostaglandin F₂.sub.α comprising reacting a biological sample containing PGF₂.sub.α with ³ H-CH₃ -CH₂ -CH₂ -CH₂ ##EQU4## isolating the labeled reaction products by thin layer chromatography and measuring the amount of radioactivity of the isolated labeled reaction products.
 8. The method of claim 7 wherein an internal standard is used.
 9. The method of claim 8 wherein the internal standard is ¹⁴ C labeled prostaglandin F₂.sub.α. 